CT scans shown to cut lung cancer death rates

Recently announced preliminary results from the National Lung Screening Trial have found that current and former heavy smokers are 20 percent less likely to die from lung cancer if they get an annual computer tomography or CT scan.

That’s remarkable news because many of the 53,000 participants in the two-year, multicenter trial are case studies for getting lung cancer – the leading cause of cancer death in the United States, claiming 157,000 lives annually, more than colorectal, pancreatic, prostate and breast cancers combined. To qualify, trial participants had to smoke 30 “pack-years” – one pack a day for 30 years or two packs a day for 15 years. Some ex-smokers who had quit within the previous 15 years were also included in the study.

We asked Dr. Eric Goodman, an associate clinical professor of radiology who served as principal investigator for the screening trial at the Moores UCSD Cancer Center, to interpret the findings.

Q: First, what’s the difference between a CT scan and a chest X-ray?

A: Both exams use ionizing radiation (X-rays) to obtain images of the chest. A CT scan obtains significantly higher resolution images of the lungs, but at a cost of increased radiation exposure. A low-dose chest CT is equivalent to 15 to 20 chest X-rays. The low-dose CT exam is a special technique developed to screen for lung cancer.

Q: Earlier analyses of X-ray use have shown that while they help catch cancers at an earlier stage, they have no effect on overall death rates. Why do CT scans appear to have such an effect?

A: With the latest generation spiral CT scanners, we are now able to routinely diagnose early-stage lung cancer. The earlier the cancer is detected, the greater chance for survival.

Q: Do the trial’s results mean every smoker should get an annual CT scan? What about former smokers or even nonsmokers?

A: When interpreting the results, you have to answer the question of “Do the risks outweigh the benefits?” In smokers, the benefits of potential early cancer detection outweigh the risks of increased radiation exposure and potential false positives (a spot in the lung that is not cancer) in this high-risk population. In nonsmokers, my guess is the risks outweigh the benefits because the incidence of cancer is low in this population. This was not studied in this trial.

Q: The trial also found that annual CT scans appear to reduce the risk of death from other causes as well? Why?

A: The reason is unknown at this time. It’s possible patients obtaining the more detailed results of a CT became motivated to modify their lifestyle, such as stopping smoking or improving diet. As emphasized by the National Cancer Institute, the best way to decrease lung cancer mortality as well as mortality from other causes is smoking cessation.